Process for the manufacture of refractory acid resisting and other products bonded by means of clay



Patented Jan. 21,- 1930 UNITED STATES PATENT OFFICE HUG-O ACKEBMANN, OF GOVESBEBG, WILHELM LANGENHEIM AND HERMANN KNUTH,

OF BONN, GERMANY PROCESS THE MANUFACTURE OF REFRACTORY ACID RESISTING AND OTHER PRODUCTS BONDED BY MEANS OF CLAY No Drawing. Application filed .Tune 17, 1926, Serial No. 116,722, and in Germany June 22, 1925.

products is to grind the grog or another nonplastic material more or less finely, and to mix it with more or less great quantities of binding clay. The comparatively greasy mass is intimately mixed with addition of water and formed into bricks or other objec'ts which are subsequently dried and burnt.

According to the special requirements which the ceramic products have to meet different non-plastic materials may be used for example chamotte (that is grog) or natural or artifical corundum, quartzite, cya-nite, sillimanite, chromite, carborundum, zirconium, magnesite, or magnesia, dolomite or alny other material, suited to be bonded by c It has been found that in the usual method of manufacturing the above mentioned products it is very diflicult to mix the non-plastic more or less coarse grained materials perfectly uniformly with the binding clay.

As a result of the non-uniform distribution of the two components in the mixture differences in shrinking occur at various points of the brick resulting in adistortion of its external shape. Further. the chemical and physical structure of the brick is not uniform, so that the resistance of the brick to high temperature, suddenchanges in temperature, chemical treatment and mechanical stresses at high temperatures is impaired.

Even when a somewhat uniform mixture is efiected by a very tedious and costly prolonging of the mixing process a considerable shrinkage both in drying and in burning occurs if large amounts of binding clay and water are added to the mixture. Usually the non-plastic components of the mixture are calcined or burnt before grinding them, so that in firing the brick they are burnt twice and therefore obtain a higher grade of transformation and consequently other physical properties than the binding clay, which is burnt only once. The greater the portion of binding clay in the brick, the greater is the unfavorable efi'ect of-the above mentioned differences between the two components .of the mixture. In using lower percentages of binding clay it has been proposed to admix clay and water to the ground non-plastic material in the form of a thin sludge, or this clay-sludge may be ground together with a small part of the non-plastic material to form a slurry which is then mixed with the rest of the ground non-plastic substance.

If an excess of water is used in preparing such masses it has further been proposed to work' the mass in heated condition, if desired in a vacuum, until the water content is reduced sufliciently to give the mass the proper consistence for moulding.

The object of the present invention is to obtain in a simple and secure way a good binding of the non-plastic materials in the manufacture of products bonded by means of clay and at the same time to use the smallest possible amount of clay. According to the invention this will be reached by mixing the binding clay in the form of a casting slip with thenon-plastic materials in such a proportion, that a non castablc mass is obtained which is moulded by beating, stamping, pressing or in any similar way likely to secure close contact between the adjoining grains of the mass It is known that a mixture of water and clay may be transformed into a casting slip .by adding a small amount of alkalies, soda quantities of non-plastlc materials, that the mass cannot be cast, but must be moulded by beating, stamping or pressing.

By its conversion into a casting slipthe binding clay is transformed into a very disintegrated mass and is converted into a dispersed state, thereby considerably increasing its binding capacity. In using this cast- 15, those hitherto used.

. proved by lime as regards strengthof binding, resistance ing slip of colloidal disintegration for the manufacture of products bonded by means of clay only a very small amount of binding clay is required and at the sanie time a thoroughly uniform distribution of the binding cla in the mixture is easily obtained. v

e inventors have found that in using the binding clay in liquefied state a very small amount of cla which according to the quality of the bin clay and the pre$ure employed inmoulding the brick may be diminlshed to 2 5% of the weight of the mass, is suflicient to maufacture clay bonded products whose qualities surpass in many regards o the products made by methods The total shrinkage of the new product is considerably reduced by the small amount of-binding clay used and the uniformity of structure of the brick is. considerably imthe good distribution of the castmg clay slip in the mixture.

The refractoriness of those products made from high refractory non-plastic materials such as corundum is importantly im roved in consequence of the small contento binding clay. The small portions of alkali which are required to convert the binding clay into a casting slip cannot impair the favorable results effected by the small content of clay as they amount. to onl about 14 91, of the quantity .of the binding clay and thus form only a small portion 0 one per cent of the total mass.

By manufacturing refractories from quartzite accordi to the new process, silica bricks bonded by c ay are obtained, which are absolutely equivalent to silica bricks bonded by to crushing, refractoriness and content of solicic 'anhydride. and su e same as regards resistance to sud en temperature changes in consequence of their superior homogeneousnes.

7 before moulding the mixtureby means of,

'ofbin If advisable the liquefied binding be transformed into a more thinly quid state by a larger quantity of water than is reqluird 'for filroducing the casting state of a c y slip. e water added in excesscanberemovedifandasfarasnecessary,

fits, for instance by heat.= Acco to procesmuch smaller rtions:

clay may be employed an was previouslfly considered possi e uniformity of the mixture or the good ofthesame.

For shaping "or moulding prepared in the manner described y mixing ground non-pladzic with a small amount of yp, y m d ybe which a very close contact the. oining grainsofthemaasisobtamed. Themass may for stampedor cla {imay le, without im- H which is suspended in the clay slip is already binding between the adjoining grains of any kind. The higher the pressure which with the mass is moulded, the better is the binding effect of the thin layer of clay-slip surrounding each grain. After drying the moulded articles may be burnt at a suitable tem ratureato cause a thorough fritting of the indi clay.

Fire brie manufactured in this way, have practically a completely homogeneous'struc ture in chemical and physical regards. They show minimum porosity and shrinkage in drying or burning. Nevertheless they have an extraordinarily good strength of binding and their resistance to crushing is greater both at low and high temperatures than that of refractory products manufactured according to the usual processes. Their resistance to changes in temperature is considerably increased as" a result of the decrease of their internal stresses.

Employing cheap non-plastic materials, for-instance ground firebrickor saggar-fragments, the use of small quantities of clay slip for binding purposes according to the mvention resultsm lowering the cost of the mixture according to the diminishing the ortion of costs, which relates to the bin g clay.

A particular method of carrying out the new process consists in not lique binding clay by itself and then mixing it with the total amount of non-plastic ground materials, but working it 'up into a slip together with a portion of the non-p astic materials and then 'mixing the slip with the rest of the latter.

In this the procedure may either be to liquefy a mixture of .clay and grog, or quartzite, or another non-plastic and material or firstly to liquefy the clay and then add to the clay slip such a portion of the ,ground non-plastic material, so that the mixture may still be casted.

" The addition of a portion of the non-plastic ground material during the preparation of the slip has the advantage that the added particles of the grog, quartzite, corund um and the-like, on treating the slip in a'stlrring device, carry out a. trituratmg on the binding clay and so accelerate and make easier the solution thereof by which means a large part of the stirring treatment and consequently time and energy is saved. The portion of the non-plastic grains,

enclosed during the preparation of. the castliquefying the binding cla way by admixing a sufiici ent quantity of.

ucts bonded by means of clay, consisting in in any known Water' and a suitable quantity of liquefying ingredients, for instance alkali, admixing the clay-slip thus obtained to the ground grog, or corundum, or quartzite, or zirconium, or any other non-plastic material fit to be bonded by means of clay, in such a proportion that a non-castable mass is obtained which is moulded by beating, stamping, pressing or in any similar way likely to secure close contact between the adjoining grains of the mass after which the moulded products are dried and burnt.

2. The process of making ceramic products bonded bymeans of clay consisting in transforming the binding clay by admixing a suitable quantity of liquefying ingredients for instance alkali and an excess of water into a diluted clay slip, the excess of water being such as to secure a thoroughly uniform distribution of small amounts of binding clay, in the mass during the subsequent mixing, admixing such a quantity of the diluted clay-slip to the ground non-plastic material as to obtain a mixture containing 10% or less of clay, removing from the mixture the excess of water as far as necessary for further treatment, moulding this mass by beating, stamping or pressing or in any similar way likely to secure close contact between the adjoining grains of the mass, after which the moulded products are dried and burnt.

3. The process of making ceramic products bonded by means of clay consisting in mixin the binding clay before, during or after its transformation into the liquefied state b admixing water and a suitable quantures.

tity' o liquefying ingredients for instance alkali w th such a part of the ground nonplastic material as to obtaina fluid slip, then mixing this slip with the rest of the ground non-plastic material in such a proportion that a non-castable mass is obtained which is moulded by beating, stamping, pressing or in any similar way likely to secure a close contact between the adjoining grains of the mass, after which the moulded dried and burnt. I 4. A refractory ceramic product consistmg of ground non-plastic ceramic material having the grains coated with a Vry'thin film of vitrified alkaline clay-slip.

' In testimony whereof we afiix our signam. In. HUGO ACKERMLANN. WILHIELM LANGENHEIM. DR. PmL. HERMANN KNUTH.

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